It was a rough year at retail for the United States video game industry.

According to the NPD Group, consumers spent 22 percent less on new video game hardware, software and accessories during the year than they did in 2011: that's $3.73 billion fewer dollars being contributed to the economy through retail video game sales.

There are several factors contributing to this, not the least of which is a quick shift to digital entertainment. Game players are spending less in stores, and spending more on their phones, tablets, computers, and the digital storefronts on their consoles.

But there's another invisible threat: what analysts are calling "gamer fatigue," as the current generation of video game consoles comes toward the end of its lifespan, and players anxiously await what's next.

Add to that the fact that far fewer games were released this year (29% fewer, in fact), and it's not hard to see why 2012 was not friendly to the industry.

Still, the biggest games continued to sell by the truckload in 2012, though even they may be declining.